Viagra patent defended

Viagra manufacturer Pfizer is defending its patent on the world-famous impotence drug.

The company has filed four lawsuits against firms attempting to produce generic impotence medication. Pfizer has two patents on Viagra: one which expires in 2012, and another that is not complete until 2019. Pfizer wants to make sure that no one manufacturers their own version of Viagra until the 2019 deadline is up.

The first patent is one of several from high profile drugs, made by various companies, which run out in 2012. The year has been deemed a "patient cliff" by some commentators.

Pfizer fears that a flood of imitation Viagra drugs will overwhelm the market, if companies are allowed to compete when the first patent runs out. The erectile dysfunction treatment brings Pfizer billions of pounds in profit every year.

Stiff competition

Since its 1998 launch, Viagra has faced competition from two other popular impotence treatments, Levitra and Cialis. Both work in a similar way to Viagra, but use different active ingredients. All three drugs have different advantages and disadvantages. Cialis lasts for longer, up to 24 hours, while Levitra may start to take effect sooner. New anti-impotence technologies being released onto the market include Levitra Orodispersable: a 'wafer' than can be placed on the tongue and dissolved into the blood stream, ensuring it gets to work fast and can be taken discreetly.

No comment from Pfizer

Last year a company spokesperson for Viagra, referring to the drug's patent running out, said: "We will not comment on future plans for Viagra. Pfizer benefits from having options when our medicines go off-patent.

"As with all our medicines, we continually explore options for patients to have access to them."